The major envelope glycoprotein, gp70, of Murine Leukemia Virus (MuLV) has been shown to be a component of normal cells and tissues, even in the absence of infectious particles. Such molecules may be of significance in normal biological processes, as originally suggested in the oncogene and protovirus hypotheses. We have shown that a unique class of MuLV gp70 was present in epididymal secretions of all mouse strains tested. Although distinct from viral gp70s, the epididymal secretion glycoprotein, gp70 (epi), is antigenically and structurally related to MuLV gp70s and represents 2-10% of the protein of these secretions. First, we will determine the relationship between gp70 (epi) and other classes of gp70. Gp70 (epi) will be purified, then used to prepare monospecific antibody. Next, we will determine the antigenic relationships among gp70 (epi), gp70s from various oncornaviruses, and molecules present in tissue from several species, including man. These assays will show the amount of gp70 (epi) in these materials as well as the extent of serological cross reaction. Further, we will study the immunologic consequences of an immune response against gp70 (epi) in unmanipulated mice and in mice immunized with purified gp70 (epi). These studies will include the development of "autoimmune" disorders such as glomerulonephritis, orchitis, epididymites. In addition, the reproductive capacity of mice immunized with gp70 (epi) will be examined by comparing sex ratio and litter size with those of control mice.